Develop Reference

Delete all rows from a mysql table

I'm trying to delete all the records from a MySQL table (46 records).
The code I have tried. Any suitable answer?
Session hs = connection.NewHibernateUtil.getSessionFactory().openSession();
Criteria cr = hs.createCriteria(Bookmark.class);
Bookmark b;
List<Bookmark> li = cr.list();
for (Bookmark s : li) {
b = new Bookmark();
b.setId(s.getId());
Transaction tr = hs.beginTransaction();
hs.delete(b);
tr.commit();
hs.flush();
hs.close();
}
Error
org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [mypojos.Bookmark#7]

You cant delete objects like that. You would first have to get the object from db and then you can delete using hs.delete(b); this is usually used when you have to cascade changes to associated objects.
Best approach in this case is to use HQL query something like this.
String stringQuery = "DELETE FROM tablename";
Query query = session.createQuery(stringQuery);
query.executeUpdate();

Query not giving solution in DAO class

when i run my query in database visualizer its working perfectly, but i think there are some issues in syntax when i convert it in my DAO class method.
I want to get whole data against the name provided
In Visualizer:
SELECT first_name,last_name,nic,phone,email FROM x_hr_user where (first_name = 'Irum');
Now in Dao
public List<XHrUser> findXHrUserByNameInTable()
{
String name ="Irum";
Query query = em.createQuery("SELECT xHrNewUserObj.firstName,xHrNewUserObj.lastName, xHrNewUserObj.nic, xHrNewUserObj.phone, xHrNewUserObj.emil FROM XHrUser xHrNewUserObj where (xHrNewUserObj.firstName) = (name)");
List<XHrUser> list = query.getResultList();
return list;
}
Instead of showing single row, it displays whole data Table
Thank you

Your current query is not valid JPQL. It appears that you intended to insert the raw name string into your query, which could be done via a native query, but certainly is not desirable. Instead, use a named parameter in your JPQL query and then bind name to it.
String name = "Irum";
Query query = em.createQuery("SELECT x FROM XHrUser WHERE x.firstName = :name")
.setParameter("name", name);
List<XhrUser> list = query.getResultList();

You have to write query as below. where : is used for variable
Query query = em.createQuery("SELECT xHrNewUserObj.firstName,xHrNewUserObj.lastName, xHrNewUserObj.nic, xHrNewUserObj.phone, xHrNewUserObj.emil FROM XHrUser xHrNewUserObj where (xHrNewUserObj.firstName) = :name");

Inner join query on Hibernate - SQL queries do not currently support iteration

I'm new to hibernate and I've this SQL query which works perfectly
SELECT count(*) as posti_disponibili from occupazione t inner join
(select id_posto_park, max(date_time) as MaxDate from occupazione
group by id_posto_park) tm on t.id_posto_park = tm.id_posto_park and
t.date_time = tm.Maxdate and t.isOccupied = 0
which gives me all the last items with isOccupied = 0
I was porting it into Hibernate, I've tried to use
result = ( (Integer) session.createSQLQuery(query).iterate().next() ).intValue()
to return posti_disponibili but i got this exception
java.lang.UnsupportedOperationException: SQL queries do not currently support iteration
How can i solve this? I cannot find the equivalent HQL query
Thank you

I would suggest you to use
Query#uniqueResult()
which will give you single result.
select count(*) .....
will always return you a single result.

Hibernate support it's own iterator-like scroll:
String sqlQuery = "select a, b, c from someTable";
ScrollableResults scroll = getSession().createSQLQuery(sqlQuery).scroll(ScrollMode.FORWARD_ONLY);
while (scroll.next()) {
Object[] row = scroll.get();
//process row columns
}
scroll.close();

How can I update specific field in database by HibernateTemplate

I want to update a specific field in the database Persons table by using HibernateTemplate. I am trying to do like this but this not working.
public void updateDate(int Id,Date receivedDate) {
Id = 10;
receivedDate = 2012-11-12;
String queryString = "update Persons set recievedDate=? where Id=? ";
getHibernateTemplate().update(queryString, new Object[] { Id, receivedDate });
}
I am getting an exception "UnkownEntity" when I run this query. Can I do update of a specific field at all by using HibernateTemplate? Is there any other alternate to do specific field update?

update method in getHibernateTemplate does not allow hql query to execute. It only allows hibernate entity object.
See link hibernate template update method
In your case Hibernate tries to resolve update Persons set recievedDate=? where Id=? as an entity.
Solution:
Query q = s.createQuery("update Persons set recievedDate=:recievedDate where Id=:Id");
q.setString("recievedDate", "some date");
q.setString("Id", "54");
q.executeUpdate();
Hope its clear.

You have to list your classes in your session factory configuration.

I assume your entity named Person
in HQL you must use java class name, not db table name

if HibernateTemplate is using, here is my solution.
// EntityName is the table to be updated
EntityName entity = hibernateTemplate.find("from EntityName where id=?" , id);
//set the value which has to be updated
entity.setValue(yourNewValue);
hibernateTemplate.SaveOrUpdate(entity);
// above updated the existing Entity table without duplicates

querying a table using JPA and populating a bean corresopind to a table

I have a project already developed using java,jsp and JPA (open jpa).Now i want to add a new API to retrieve data from DB.Am not much familiar with JPA.Now i want to take a join of 3 tables Atbl , Btbl, and Ctble ,then check for some conditions and finally populate bean corresopnding to table Atble.I saw a a API as follows
String sql = "SELECT A.* FROM Atble A, Btbl B WHERE A.xyz = B.pqr
AND A.field1 = ? AND B.field2 = 'SubComponent' AND B.field3 = ? ";
Query q = em.createNativeQuery(sql, A.class);
q.setParameter(1,"aa");
q.setParameter(2, "aa");
q.setParameter(3, "cc");
List<A> a = (List<A>) q
.getResultList();
Does it populate bean for A directly?If not how can i populate bean for A

This will return a List, so should work fine.
You may also consider using JPQL instead of a native SQL query, but if you are more comfortable with SQL that is fine.